Adam Clarke on Exodus 4:13

Send - by the hand of him whom thou wilt send - Many commentators, both ancient and modern, have thought that Moses prays here for the immediate mission of the Messiah; as if he had said: "Lord, thou hast purposed to send this glorious person at some time or other, I beseech thee send him now, for who can be sufficient to deliver and rule this people but himself alone?" The Hebrew שלח נא ביד תשלח shelach na beyad tishlach literally translated is, Send now (or, I beseech thee) by the hand thou wilt send; which seems to intimate, Send a person more fit for the work than I am. So the Septuagint: Προχειρισαι δυναμενον αλλον, ὁν αποστελεις· Elect another powerful person, whom thou wilt send. It is right to find out the Messiah wherever he is mentioned in the Old Testament; but to press scriptures into this service which have not an obvious tendency that way, is both improper and dangerous. I am firmly of opinion that Moses had no reference to the Messiah when he spoke these words.